1. Field of the Invention
This invention relates to speed warning devices and, more particularly, to a speed warning device which may be added to an existing speedometer installation.
2. Description of the Prior Art
Some vehicle speedometers are provided, usually as an extra cost option, with a speed warning device which serves to give an audible warning in the event that a certain speed is reached or exceeded. Such systems as are known generally include a first electrical contact, generally fixed in position and a second electrical contact mounted for movement with the speedometer pointer, so as to complete an electrical circuit to energize an associated audible alarm mechanism by touching the first contact when the speedometer pointer reaches a predetermined speed indication. In some instances the position of the first contact is adjustable and may be set by means of a knob extending outside the speedometer casing. Examples of such prior art systems are to be found in the Fairhurst U.S. Pat. No. 2,433,895 and the Matsumura U.S. Pat. No. 3,713,093. Some speed sensing systems are more elaborate and incorporate means for controlling the speed of an automobile within a pre-set range through the sensing of the position of the speedometer pointer or an element movable therewith. Such a system is disclosed in the Teves U.S. Pat. No. 1,453,368. Systems similar to te speed warning systems of the prior art are applicable to tachometers, which indicate engine RPM's. Such a system for tachometers is disclosed in the Magid U.S. Pat. No. 2,728,072.
As indicated, all such systems as are known involve the incorporation of special equipment within the speedometer unit which must either be installed on the vehicle as original equipment or must be substituted for the originally installed speedometer by retrofitting to the vehicle at considerable effort and expense. Heretofore it has been a desirable feature to have the capability of adjusting the speed at which the alarm will be sounded. This is because the maximum speeds established by law have varied substantially from state to state and even within a state have varied from highways to freeways, turnpikes or the like. Now, however, because of the imposition of federal controls as a result of the recent oil embargo and increased emphasis on conservation of petroleum resources, the maximum speed throughout the United States have been established at 55 miles per hour. This speed is substantially less than the speed at which drivers are accustomed to driving in many areas of this country and therefore it becomes more important than ever to provide some sort of a warning device to indicate to the driver of an automobile or his passengers when the vehicle is exceeding the standard speed limit. At the same time, it is no longer important to be able to vary the point at which the speed warning will be sounded. Most drivers would be satisfied to have the warning fixed at 55 miles per hour. However, with such systems as are known in the prior art, the cost of retrofitting vehicles with such speed warning systems is prohibitively expensive and therefore very few automobile owners will install such equipment on their vehicles, despite the increased need for a speed warning system. What is needed is simple, low-cost, effective and reliable speed warning system which may be installed on existing speedometer equipment with a minimum of effort and expense and without interfering with the effective operation of the speedometer.